1. FIELD OF THE INVENTION
This invention relates to method and apparatus for preparing crimped fibrous structures and more particularly to means for crimping textile fibrous materials such as filaments, yarn, tow for staple fibers and the like.
2. DESCRIPTION OF THE PRIOR ART
In the apparatus conventionally used to crimp textile strands to increase their bulkiness, a tow of continuous filaments is forced by fluid energy against a mass of tow within a chamber, and emerges in crimped form from the chamber when the pressure on the mass exceeds a certain limit. The number of crimps produced by such apparatus per inch of the filaments, as well as the skein shrinkage or crimp contraction level produced in the filaments, is too low for economical processing of the filaments into high quality knitting yarns, fabrics, high stretch yarns and the like. Higher fluid temperatures, as in the order of 400.degree. C., increase crimping levels but decrease orientation of the filaments, reducing their tensile strength and/or dyeing uniformity. Increasing mass flow of the fluid to heat the yarn at lower fluid temperatures produces turbulence within the chamber, destroying incipient crimp and decreasing the skein shrinkage level of the filaments.